| Summary: | In this study we surveyed a rat skeletal muscle RNA-Seq for genes that are induced by hindlimb immobilization and, in turn, become attenuated by leucine supplementation. This approach, in search of leucine-atrophy protection mediating genes, identified histone deacetylase 4 (<i>HDAC4</i>) as highly responsive to both hindlimb immobilization and leucine supplementation. We then examined the impact of leucine on <i>HDAC4</i> expression, tissue localization, and target genes. A total of 76 male Wistar rats (~280 g) were submitted to hindlimb immobilization and/or leucine supplementation for 3, 7 and 12 days. These animals were euthanized, and soleus muscle was removed for further analysis. RNA-Seq analysis of hindlimb immobilized rats indicated a sharp induction (log2 = 3.4) of <i>HDAC4</i> expression which was attenuated by leucine supplementation (~50%). Real-time PCR and protein expression analysis by Western blot confirmed increased <i>HDAC4</i> mRNA after 7 days of hindlimb immobilization and mitigation of induction by leucine supplementation. Regarding the <i>HDAC4</i> localization, the proportion of positive nuclei was higher in the immobilized group and decreased after leucine supplementation. Also, we found a marked decrease of myogenin and <i>MAFbx</i>-<i>atrogin-1</i> mRNA levels upon leucine supplementation, while <i>CAMKII</i> and <i>DACH2</i> mRNA levels were increased by leucine supplementation. Our data suggest that <i>HDAC4</i> inhibition might be involved in the anti-atrophic effects of leucine.
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